The present invention relates an optical system for detection of clear air turbulence (CAT), high altitude ice crystals (HAIC), and volcanic ash clouds (VAC) in a three channel system.
CAT, HAIC, and VAC all may posed a threat or discomfort for aircraft in flight. For example, atmospheric ice-particles may pose a threat for engines of aircraft in flight. Ice-particles from HAIC may get into aircraft engines and attach themselves to engine surfaces, building up until ice causes engine failure in some way. The ice particles typically are present in the atmosphere in the form of ice-particle aerosols.
CAT is the turbulent movement of air masses in the absence of any visual cues such as clouds, and is caused when bodies of air moving at widely different speeds meet. The atmospheric region most susceptible to CAT is the high troposphere at altitudes of around 7,000-12,000 meters (23,000-39,000 ft) as it meets the tropopause. Here CAT is most frequently encountered in the regions of jet streams. At lower altitudes it may also occur near mountain ranges. Thin cirrus clouds can also indicate a high probability of CAT.
CAT can be hazardous to the comfort, and even safety, of air travel. The thermal characteristics of CAT are known. Studies show that gust velocity changes in CAT of at least 20 ft sec−1 are associated with temperature changes of 3° C. or higher; very few being less than 1° C. Such studies show that CAT horizontal temperature gradients with a minimum temperature change of 2° C., and at a rate which equaled or exceeded 0.5° C. per minute. Moderately choppy CAT was observed at a 5° C. temperature change
Finally, volcanic ash from VAC may also pose a threat or discomfort for aircraft in flight. VAC can appear instantaneously while an aircraft is in flight, even in the dark, and may be hazardous to aircraft flight through consequent engine failure/damage.
What is needed is an optical system for detecting CAT, HAIC and VAC in a single system.